Emerging ultra low-power applications such as wireless sensor networks and wireless body area networks require the integration of very efficient signal processing techniques, specifically in analog-to-digital conversion. General-purpose ADCs which rely on Nyquist theory result in unnecessary sampling, and dissipate excessive power within the ADC and subsequent digital signal processing units during periods of low activity.
Activity dependent (see Schell, B., Tsividis, Y.: ‘A continuous-time ADC/DSP/DAC system with no clock and with activity-dependent power dissipation’, IEEE J. Solid-State Circuits, 2008, 43, (11), pp. 2472-2481) (hereinafter “Reference [1]”), variable resolution (see Kurchuk, M., Tsividis, Y.: ‘Signal-Dependent Variable-Resolution Clockless A/D Conversion with Application to Continuous-Time Digital Signal Processing’, IEEE Transactions on circuits and systems I, 2010, 57, (5), pp. 982-991) (hereinafter “Reference [2]”), ADCs, and continuous time digital signal processing (see Tsividis, Y.: ‘Continuous-time digital signal processing’, Electron. Lett., 2003, 39, (21), pp. 1551-1552 (hereinafter “Reference [3]”) are the most recent techniques to tackle the aforementioned issues.
Prior art includes the following publications: WO 2011/046928, US 2004/263375, WO 2005/004373, WO 2006/063192, EP 2298164, WO 2006/039510, U.S. Pat. No. 7,839,317, US 2008/252280, US 2010/270989, WO 2007/036922, US 2007/216466.